The following account of the prior art relates to one of the areas of application of the present application, hearing aids, and in particular to the fitting of hearing aids to a particular user's needs.
A fitting rationale (algorithm) is used by a hearing care professional (HCP, e.g. an audiologist) to determine gain versus frequency for a particular hearing impairment and a particular person (ear/hearing aid). A fitting algorithm, such as NAL-RP, NAL-NL2 (National Acoustic Laboratories, Australia), DSL (National Centre for Audiology, Ontario, Canada), ASA (American Seniors Association), etc., is generally used for this purpose. Among the inputs to such fitting algorithms are hearing threshold or hearing loss data (e.g. based on an audiogram), comfort level, for the user in question, type of hearing aid, etc. Further, a so-called real-ear-to-coupler difference (RECD) measure can be used to fine tune the gain setting, in particular for children (and in particular for relatively closed fittings comprising an ear mould). RECD is defined as the difference in dB as a function of frequency between a sound pressure level (SPL) measured in the real-ear (of the particular user) and in a standard 2 cm3 (often written as 2-cc) acoustic coupler, as produced by a transducer generating the same input signal in both cases. Since the ear canal of a user varies with age (in particular during growth of a child, but also for adults), RECD values vary as a function of frequency as well as time (e.g. age).
When a hearing care professional wants to perform a real ear measurement, it is known (cf. e.g. U.S. Pat. No. 7,634,094) that it can be done easier and faster by using the hearing aid itself to perform the measurement. U.S. Pat. No. 7,634,094 teaches a method for measuring an audio response of a real ear using the microphone of a hearing aid of the user. In that way, it is not necessary to use additional equipment, and for some types of measurements (e.g. RECD measurements) it is considered more precise, since the acoustic environment of the hearing aid (comprising a customized housing (mould)), when performing the measurement, is identical to the acoustical environment, when normally using the hearing aid.
The problem for any type of real ear measurements is to eliminate the noise, and get better signal to noise ratio (SNR). Any improvement of the SNR will result in a more reliable, and probably also a faster, measurement, if less averaging of measurements are needed.